Softening of water and the flocculation of suspended solids in aqueous liquids



'i'atented' July 18, 1944 UNITED STATES PATENT clerics v sor'rnmsa or w si' isn THE snoccuass. autis rm m John- Oswald Samuel, Swansea, Wales, assignor to Uniiioe Reagents Limited,

a British company No Dra Swansea, Wales,

wing. application February 20. 1940, Serial No. 319,988. Divided and this'al plication February 28, 1941-. Serial No. 381,002. In Great Britain February 23,1939

1: Claims. (cl. 215-23) 7 The present invention is ior improvements in or relating to water softening and for the flocculation of suspended solids in aqueousliquids and includes the flocculation of suspended solids in water softening and in the clarification of efliucuts and certain trade wastes.

This application is divided from my United about 110' o. the paste formed is immediately convertedintoahardmassthatcanbebroken up into powder or, if the paste is continuously V stirred during the addition of starch, a powdery States patent application Serial No. 319,983, flled February 20, 1940.

In the softening of water, the addition of milk of lime and/or soda ash to cold hard water to precipitate out dissolved salts as carbonates possesses certain disadvantages. 4 over the theoretical quantity ofreagent. or reagents, such as lime and/or soda ash has invariably to be added in order to reduce the hardness to a low figure; in the absence of heat the reaction does not usually proceed to completion; an excess of reagents gives a softened water with a high degree of alkalinity; the precipitates are in most cases diillcult to remove by filtration; and there is a tendency for after-precipitation particularly with water containing appreciable quantities of magnesium salts.

It is an object of the present invention to pro vide a process of water softening which minimises Thus, an excess the above-mentioned disadvantages by the employment or a new reagent described and claimed 7 in my co-pending United States patent application Serial No. 319,983.

According to the present invention the process for softening water and for the flocculation oi solids suspended therein comprises mixing with the water alkali such as lime and/or soda ash and a proportion of a reagent prepared by reacting aluminium sulphate (or a mixture of sodium or potassium aluminate and sodium or potassium sulphate) and caustic soda orvcaustic potash and adding starch to the reaction mixture at or above room temperature but not exceeding about 140 C. This temperature is attained by the reaction of the aluminlumsulphate withcaustic soda or 1 gallons of the suspension to be treated. The quancaustic potash, the reaction being carried outonly with such external heating. asis necessary to initiate the reaction or by the direct heating" of the alkali aluminate and caustic alkali.

When the starch is added to the reaction mixture at or about room temperature the paste formed sets onstanding to a comparatively hardmass which can be broken up and powdered; At temperatures between room temperature and product is formed without the intermediate hard mass and therefore no subsequent breaking up of the product is re'quired' The setting or the paste may take as long as two or three hours at 30- i0f C. and approximately 10 7 minutes at 60 C,

The aluminium sulphate may contain water oi .to the'water to be softened together with the usual softening chemicals employed inthe Clark process oi water softening, via. lime and/or soda ash and this alkali is referred toin the appended claims as alkali as herein defined. 'The water is softened to a low figure or hardness, for example down to one or two degrees within approximately one hour from the time oi introduction of the reagent into the water. The precipitate forms immediately and assumes a flocculated form and settles rapidly, leaving a clear soit water with a low degree of alkalinity.

When the reagent is added. preferably in the form of a. dilute solution or suspension, to aqueous suspensions oi inter alia coal slurry, clays such as Bentonite, ganister, china clay, flue dust,

vegetation, paper pulp and the like, excellent nocculation is obtained on'the addition of approximately 0.25-lb. in 1.0 lb. of the reagent per 1,000

tlty to be added depends on the conditions. In order to obtain the best results it is important that the suspensions should be made alkaline, e. g., with lime before adding the reagent. The quantity of alkali which should be added to a suspension prior to flocculation in accordance with this invention is approximately 0.5,to 4 lbs. per 1,000 gallons. The concentration of the suspensions for flocculation is assumed tobe oi such an order that the flocculated particles have reasonably free falling conditions. Thus a coal slurry suspension should contain solids oi the order of 5 to 10% clay, e. g., 5% of solids, and vegetation and pulp suspensions 0.10% to 0.50% approximately. I

' The water softening may be carried out by either a hot or a cold process, The amount oi added reagent may be of the order of 0.1 to 0.4 lb.

per 1,000 gallons of water and may amolmt to 2% to 8% on the weight of the calcium hydroxide or the combined weight of the calcium hydroxide and soda ash employed.

The following table indicates the results obtained by using the product of the invention in conjunction with soda ash and calcium hydroxide with four difl'erent, samples of hard water:

1. A process for the softening of water and the flocculation of solids suspended therem which process comprises adding to the water to be treated an amount equal to 0.5 to 4 lbs. per 1,000 gallons of the said water of an alkali as herein defined and mixing with the water 0.1 to 1 lb. per 1,000 gallons of the said water of a reagent produced by reacting together substantially equal amounts of aluminum sulphate (A1z(SO4)3.12H:O) and an alkali metal hydroxide at a temperature not exceeding 140 C. and adding starch to the reaction mixture at a temperature not below room temperature and not exceeding 140 C. and removing the precipitate from the water.

2. A process for the softening of water and for the flocculation of solids suspended therein which process comprises adding to the water to be treated an amount equal to 0.5 to 4 lbs. per 1,000 gallons of the water. to be treated of an alkali as herein defined and mixing with the water 0.1 to 1 lb. per 1,000 gallons of the said water of a reagent produced by reacting together substantially equal amounts of aluminum sulphate (1112(804) 1.12340) and caustic potash at a temperature not exceeding 140 C., adding starch to the reaction mixture at a temperature not below room temperature and not exceeding 140 C. and removing the precipitate from the water.

3. A process for the softening of water and for the flocculation of solids suspended therein which process comprises adding to'the water to be treated an amount equal to 0.5 to 4 lbs. per 1,000 gallons of the water to be treated 01' an alkali as herein defined and mixing with .the water 0.1 to 1 lb. per 1,000 gallons of the said water of a reagent produced by reacting together substantially equal amounts of aluminum sulphate (Al:(SO4):.l2H:O) and caustic potash at a temperature not exceeding 140 C., adding starch to the reaction mixture at a temperature not below room temperature and not exceeding 140' C. and removing the precipitate from the water.

4. A process for the softening of water and the flocculation of solids suspended therein which process comprises adding to the water to be treated an amount equal to 0.5 to 4 lbs. per 1,000 allons of the said water of an alkali as herein defined and mixing with the water 0.1 to 1 lb.

. reaction mixture and removing the produced by reacting together substantially equal amounts of aluminum sulphate (AlflSOi) 3.121110) and an alkali metal hydroxide at a temperature not exceedin 140 C., cooling thegeaetion mixture to 30 to 60 C. and adding starch to the the precipitate from the water.

5. A process for the softening of water and flocculation of solids suspended therein which process comprises adding to the. water to be treated an amount equal to 0.5 to 4 lbs. per 1,000 gallons of the said water of an alkali as herein defined and mixing with the water 0.1 to 1 lb. per 1,000 gallons of the said water of a reagent produced by reacting together substantially qual amounts of aluminum sulphate (A1:(SO4):.12H:O) and caustic potash at a temperature not exceeding 140 C., cooling the reaction mixture to 30 to 60 C. and adding starch to the reaction mixture and removing the prev cipitate from the water.

at a temperature 6. A process for the softening'of water and the flocculation of solids suspended therein which process comprises adding to the water to be treated an amount equal to 0.5 to 4 lbs. per 1,000 gallons of the said water of an alkali as herein defined and mixing with the water 0.1 to 1 lb. per 1,000 gallons of the said water of a by reacting together substannot exceeding 140 C., cooling the reaction mixture to 30 to C. and incorporating in the said reaction mixture dry starch in amount substantially one-half that of the aluminum sulphate or alkali metal hydroxide and removing the precipitate from the water.

7. A process for the softening of water and the flocculation of solids suspended therein which process comprises adding to the water to be treated an amount equal to 0.5 to 4 lbs. per 1,000 gallons of the said water -of an alkali as herein defined and mixing with the. water 0.1 toil lb. per 1,000 gallons of the said water of a reagent produced by reacting together aluminum sulphate and an alkali metal hydroxide, the amount of the alkali hydroxide being between 62 and on the weight of the aluminum sulphate (calculated as A12(S04)3.12H20) and inco porating in the reaction mixture starch at a temperature up to C. and in proportion substantially between 15 and 30% by weight on the combined weight of the aluminum sulphate and the alkali metal hydroxide, and removing the precipitate from the water.

8. A process for the softening of water and the flocculation of solids suspended therein which process comprises adding to the wafer to be treated an amount equal to 0.5 to 4 lbs. per 1,000 allons of the said water of an alkali as herein defined and mixing with the water 0.1 to 1 lb. per 1,000 gallons of the said water of a reagent produced by reacting together sodium aluminate, so-

' dium sulphate and an alkali metal hydroxide, th

per 1,000 gallons of the said-water of a reagent 7s alkali metal hydroxide bealkali metal hydroxide and sodium aluminate and sodium sulphate, allowing the product to cool and set to a hard mass and grinding the said mass to powder and removing the precipitate from the water.

9. A process for the softening of water and flocculation of solids suspended therein which processcomprises adding to the water to be treated an amount equal to 0.5 to 4 lbs. per 1,000

gallons of the said water of an alkali as herein defined and mixing with the water 0.1 to 1 lb. per

tially one-half that of the aluminum sulphate or alkali metal hydroxide and removing the precipitate from the water. I

A process for the softening of water and the flocculation of solids suspended therein which process comprises adding to the water to be treated an amount equal to 0.5 to 4lbs. per 1,000 gallons of the said water of an alkali as herein defined and mixing with the water 0.1 to 1 lb. per 1,000 gallons of the said water of a reagent produced by reacting together substantially equal amounts of aluminum sulphate (A12(SO4) 3121-120) and an alkali metal hydroxide at a temperature not exceeding 140 C. and adding to the reaction mixture 1 to 10% by weight of soft soap on the weight of the reaction mixture and incorporating in the said reaction mixture starch in amount substantially one-half that of the aluminum sulphate or alkali metal hydroxide and removing the precipitate from the water. I

11. A process for the softening of water and the flocculation of solids suspended therein which process comprises adding to the water to be treated an amount equal to 0.5 to 4 lbs. per 1,000 gallons of the saidwater of an alkali as herein defined and mixing with the water 0.1 to 1 lb.

per 1,000 gallons of the; said water of a reagent produced by reacting together substantially equal amounts of aluminum sulphate (A12(SO4)3.12H2O) and an alkali metal hydroxide at a temperature not exceeding 140 C. and adding to the reaction mixture 0.5 to 5% by weight of hard soap on the weight of the reaction mixture and incorporating starch in the mixture in amount substantially one-half that of the aluminum sulphate or alkali metal hydroxide and removing the precipitate from the water.

12. A process for the softening of water and the flocculation of solids suspended therein which process comprises adding to the water to be treated an amount equal to 0.5 to 4 lbs. per 1,000 gallons of the said water of an alkali as herein defined and mixing with the water 0.1 to 1 lb. per

1,000 gallons of the said water of a reagent produced by reacting together substantially equal amounts of aluminum sulphate (A12(SO4) 3.12H2O) and an alkali metal hydroxide at a temperature not exceeding 140 C. and adding to the reaction mixture a substance selected from the group consisting of dialkali phosphate and trialkali phosphate in amount equal to 5% by weight on the weight of the reaction mixture and incorporating starch in the mixture in amount substantially one-half that of the aluminum sulphate or alkali metal hydroxide and removing the precipitate from the. water.

13. A process for the softening of water and the flocculation of solids suspended therein which process comprises adding to the water to be treated an amount equal to 0.5 to 4 lbs. per 1,000 gallons of the said water of an alkali as herein defined and mixing with the water 0.1 to 1 lb. per

1,000 gallons of the said water of a reagent produced by reacting together substantially equal amounts of aluminum sulphate (A12(SO4) 3.12H2O) and, an alkali metal hydroxide at a temperature not exceeding C. and adding starch to the reaction mixture at a temperature not below room temperature and not exceeding 140 C. the amount of starch being substantially one-half that of the aluminum sulphate or alkali metal hydroxide and incorporating in the product a proportion of lime and removing the precipitate from the water.

JOHN OSWALD SAMUEL. 

